Vol.66 No.6 November 2018
Diagnosis and treatment of rickettsioses in Japan: tsutsugamushi disease and Japanese spotted fever
1)Department of Infection Control and Prevention, Faculty of Medical Sciences, University of Fukui, 23-3 Matsuoka-Shimoaizuki, Eiheiji, Fukui, Japan
2)First Department of Internal Medicine, Faculty of Medical Sciences, University of Fukui
Abstract
Tsutsugamushi disease is a mite-borne infectious disease transmitted by the bite of the larvae of a small tick (tsutsugamushi) harboring a pathogenic rickettsia species, Orientia tustsugamushi. O. tustsugamushi is serologically diverse in Japan, and is classified into 6 serotypes. We have detected the 3 standard types of Gilliam, Karp and Kato, and 3 new types of Irie/Kawasaki, Hirano/Kuroki, Shimokoshi, have been increasingly isolated from patients in recent years. The number of reported cases in Japan is approximately 400 to 500 cases per year, and the areas of occurrence cover all national prefectures of Japan, except Hokkaido. The season of onset coincides with the moving activity period of the tsutsugamushi, and the disease mainly occurs from the autumn to early winter months or the spring to early summer months. In Japan, any cases of rickettsioses diagnosed need to be reported by the attending doctors to the appropriate public health center.
Japanese spotted fever is transmitted by the bite of the larvae of a tick harboring the rickettsia sp., Rickettsia japonica. A total of 215 cases was reported in 2015, 275 cases in 2016, and 337 cases in 2017; thus, it is on an increasing trend. The season of onset coincides with the moving activity period of the ticks, the disease occurring mainly from April to November, and also frequently from the summer to autumn months. In addition, the infection occurs mainly in the relatively mild coast of the Pacific Ocean, west of the Kanto region, although it has also spread to the northern areas in recent years. Recently, new pathogenic species, such as R. heilongjiangensis, R. helvetica and R. tamurae, have also been isolated, and in Japan, the geological aspect of the spotted-fever group of rickettsioses is continually diversifying. Doctors diagnosing this disease also need to report each case to the appropriate public health center.
Tetracyclines are used as the drugs of first choice for treatment, and they have also been recognized as being effective against tsutsugamushi disease. However, tetracyclines do not appear to exert sufficient efficacy against Japanese spotted fever. Quinolones combined with a tetracyclines is the candidate anti-rickettsial chemotherapy for Japanese spotted fever. Further investigation is needed to establish an appropriate treatment for this disease.
Key word
rickettsiosis, tsutsugamushi disease, Japanese spotted fever, tick-borne disease
Received
April 5, 2018
Accepted
May 9, 2018
Jpn. J. Chemother. 66 (6): 704-714, 2018
